COMMITMENTS AND CONTINGENCIES: - Litigation matters (Details)	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2016 lawsuit	Jun. 30, 2015 lawsuit item	Dec. 31, 2020 claim item lawsuit	Dec. 31, 2015 item lawsuit	Dec. 31, 2019 item	Dec. 31, 2018 lawsuit
Litigation Matter
Number of collective action lawsuits		6
Number of subsidiaries against which lawsuits were filed | item		2
Number of collective action lawsuits dismissed		2
Number of lawsuits in process			4
Number of civil actions seeking damages						33
Number Of Constitutional Action Lawsuits				4
Number of subsidiaries to which environmental impact authorizations were granted | item				1
Tia Maria
Litigation Matter
Number of lawsuits			5
Buenavista del Cobre, S.A. de C.V
Litigation Matter
Number of civil actions seeking damages				8	3	3
Number of resolutions | claim			45
Francisca Garcia Enriquez
Litigation Matter
Number of additional constitutional lawsuits filed				2
Mario Alberto Salcido et al; Maria Elena Heredia Bustamante et al; Martin Eligio Ortiz Gamez et al and Maria de los Angeles Enriquez Bacame et al
Litigation Matter
Number of additional constitutional lawsuits filed	4
Mario Alberto Salcido et al; Maria Elena Heredia Bustamante et al; Martin Eligio Ortiz Gamez et al and Maria de los Angeles Enriquez Bacame et al | Mexico
Litigation Matter
Number of monitoring wells downstream from the dam | item			3
Period to submit Semarnat			2 years
Norberto Bustamante et al
Litigation Matter
Number of additional constitutional lawsuits filed			2
Acciones Colectivas de Sinaloa
Litigation Matter
Number of lawsuits in process			3